NMR Spin Relaxation to probe Side-Chain Dynamics in IDPs

Proteins fulfill diverse functions and are thus crucial and essential components of living organisms. It is common belief that the three-dimensional (3D) structure determines the chemical and biological functionalities of proteins as the unique 3D arrangement of distinct chemical groups allows the protein to bind to and engage with diverse binding partners. This concept was first formulated by Emil Fischer (Lock-and-Key Principle) and has dominated biological research throughout the 20th century. The founding moment of structural biology was when Max Perutz and John Kendrew determined the first protein structures. The obtained protein structural information provided detailed insight into how enzymes (Natures robots, C.Tanford) can perform their challenging chemical tasks and catalyze chemical reactions under mild physiological conditions. The field of structural biology has recently experienced another tremendous boost by the development of artificial intelligence (AI) based algorithms for the prediction of protein structures. Despite its tremendous success in the past, however, the concept of static (rigid) protein structures was severely questioned with the recent identification of intrinsically disordered proteins (IDPs). They have attracted a lot of attention, as in contrast to their stably folded counterparts IDPs feature a rather flexible nature and exist in numerous different structures (conformations). The structural flexibility endows IDPs with enormous potential to simultaneously interact with and control multiple binding partners and maintain complex protein interaction networks. The lack of a stable, rigid three-dimensional structure requires a suitable experimental technique to probe the subtleties of the dynamic interconversion of different protein conformations (structures). Nuclear magnetic resonance (NMR) spectroscopy offers unique possibilities for structural and dynamic studies of IDPs and has already provided unique insight into the conformational ensembles sampled by IDPs in solution. The main goal of the proposed research project is to develop and apply novel NMR spectroscopic tools for structural and dynamic studies of intrinsically disordered proteins (IDPs) and their complexes. We plan to develop novel NMR techniques for probing the time- dependence of spatial relationships between different parts of an IDP. Although some NMR experiments have been developed in the past for the protein backbone similar techniques for protein side-chains are missing. The intended project will fill this technological gap and thus considerably increase the arsenal of techniques to study the subtleties of this important protein family. In a first example, we will apply these techniques to an extracellular matrix IDP Osteopontin, a cytokine relevant for inflammatory processes and tumor progression. The principal investigator of the project is Prof. Robert Konrat, Department of Structural and Computational Biology, University of Vienna.